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Adequate Models (adequate + models)

Distribution by Scientific Domains

Life Sciences	40%

Selected Abstracts

How to go extinct: lessons from the lost plants of Krakatau

JOURNAL OF BIOGEOGRAPHY, Issue 5 2000
Robert J. Whittaker
Abstract Aim Few data sets exist that allow measurement of long-term extinction and turnover rates for islands of the size of the three main islands of the Krakatau group. We test the reliability of previous estimates of plant species extinction and examine structure within the extinction data. Location The data analysed are for the three older Krakatau islands: Rakata, Sertung and Panjang in the Sunda Strait, Indonesia. Methods Our analysis is based on a comprehensive database incorporating all species records for each island since recolonization began after the 1883 sterilization, plus attributes such as distribution, phylogeny, population status and dispersal mechanism for each species. We employ a combination of univariate and multi-term analyses in analysing structure, and derive Minimal Adequate Models using binary logistic analyses of variance and covariance. We compare the 1883,1934 data set with the contemporary flora as represented by (1) 1979,83 records (as used in previous analyses) and (2) 1979,94 data (original). Results The improved data for the contemporary flora reduces the number of missing species by one-third. We show that a variety of estimates of extinction rate can be produced depending on what assumptions are made concerning the status of particular species groups. Structural features in the extinction data persist despite the reduction in overall numbers of losses. Losses relate to: (1) the number of islands on which a species originally occurred, (2) the primary dispersal mode, and (3) the original abundance of a species (e.g. whether it was known to have established a successful resident population, and whether it was in decline or increasing in c. 1930). The ,best' descriptive model employs the variables denoted under (3). A high proportion of losses comprised species introduced by people and rare or ephemeral species. Losses of ,residents' that had colonized naturally could largely be accounted for by reference to (1) successional loss of habitat and, to a lesser degree, (2) other habitat disturbance or loss. Main conclusions Previous analyses, based on a more limited data set, have significantly over-estimated extinction from the Krakatau flora. Few naturally colonizing and established species have become extinct. The findings indicate that caution is necessary in interpreting ,headline' island ecological rates, and in analysing and modelling such data. Examination of structural features of the data appear to be valuable both in providing ecological insights in their own right, and in enabling refinements to estimates of extinction and thus turnover. [source]

Diversity of native and alien plant species on rubbish dumps: effects of dump age, environmental factors and toxicity

DIVERSITY AND DISTRIBUTIONS, Issue 3 2003
Antonín Py
Abstract. The flora of 96 rubbish dumps consisting of organic, inorganic and industrial wastes was studied in the Czech Republic. Some dumps contained toxic substances (heavy metals, chlorethylenes, phenols, polychlorinated biphenyls, oil hydrocarbons and biogas). Statistically significant factors explaining the number and proportional representation of native plant species, archaeophytes (introduced before 1500) and neophytes (introduced later) were determined. In total, 588 species of vascular plants were recorded, with archaeophytes (133 species) over-represented and native species (322 species) and neophytes (133 species) under-represented compared to their proportions in the national flora. Minimum adequate models were used to determine the effects of several factors on species numbers and proportions, independent of other factors. Dump area, human density in the region and altitude (non-significant only in archaeophytes) were correlated positively with species numbers. Dump age, expressed as time since dump establishment, interacted with the dump toxicity; species numbers increased with dump age on non-toxic dumps, whereas on toxic dumps no increase in numbers was noted. For neophytes, dump toxicity also interacted with human density; the increase in numbers of neophytes with human density is more pronounced on toxic than on non-toxic dumps. The variables measured failed to explain observed differences in proportional representation of native species, archaeophytes and neophytes. This suggests that the occurrence of species growing in such extreme habitats is driven overwhelmingly by factors such as anthropogenic disturbance. A possible explanation for the positive effect of altitude on species numbers on dumps is that the effect of heating of the deposited substrate by microbiological processes, documented by previous studies, overrides the effect of altitude which was shown repeatedly to have a negative effect on species richness. Neophyte distribution is driven by an interplay of factors distinct from those influencing the distribution of native species, namely toxicity and human density (the latter we interpret as a surrogate for propagule pressure). Their distribution on studied dumps is more restricted than that of native taxa and archaeophytes, and they are more limited by toxic substrata; more intensive propagule pressure is required for their establishment at dumps with higher toxicity levels. [source]

RECONSTRUCTING DEWEYAN DEMOCRATIC EDUCATION FOR A GLOBALIZING WORLD

EDUCATIONAL THEORY, Issue 4 2009
Jessica Ching-Sze Wang
As democratic citizenship education gains importance worldwide, one wonders whether common civic education practices in the United States, such as mock elections, are adequate models for other countries, or whether they fall short of realizing the goal of promoting democracy in different regions and cultures. Despite various controversies, one fundamental question remains: How should we teach democracy? Should we teach it as a system of government or as a way of life? Jessica Ching-Sze Wang finds inspiration in Dewey's life and works. She draws on Dewey's experience during the First World War and his insights into the connection between democracy and education to reconstruct a culturally and morally robust form of democratic education, as opposed to the politically dominated one currently being practiced. Wang concludes that Deweyan democratic education thus reconstructed can help us better realize democracy as a way of life for our globalizing world. [source]

Agricultural soils spiked with copper mine wastes and copper concentrate: Implications for copper bioavailability and bioaccumulation,

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2006
Rosanna Ginocchio
Abstract A better understanding of exposure to and effects of copper-rich pollutants in soils is required for accurate environmental risk assessment of copper. A greenhouse experiment was conducted to study copper bioavailability and bioaccumulation in agricultural soils spiked with different types of copper-rich mine solid wastes (copper ore, tailing sand, smelter dust, and smelter slag) and copper concentrate. A copper salt (copper sulfate, CuSO4) that frequently is used to assess soil copper bioavailability and phytotoxicity also was included for comparison. Results showed that smelter dust, tailing sand, and CuSO4 are more likely to be bioavailable and, thus, toxic to plants compared with smelter slag, concentrate, and ore at equivalent total copper concentrations. Differences may be explained by intrinsic differences in copper solubilization from the source materials, but also by their capability to decrease soil pH (confounding effect). The copper toxicity and bioaccumulation in plants also varied according to soil physicochemical characteristics (e.g., pH and total organic carbon) and the available levels of plant nutrients, such as nitrogen, phosphorus, and potassium. Chemistry/mineralogy of mine materials, soil/pore-water chemistry, and plant physiological status thus should be integrated for building adequate models to predict phytotoxicity and environmental risk of copper. [source]

Dynamics of the solar magnetic field from SOHO/MDI

ASTRONOMISCHE NACHRICHTEN, Issue 1 2010
E.E. Benevolenskaya
Abstract The investigation of the dynamics of magnetic fields from small scales to the large scales is very important for the understanding of the nature of solar activity. It is also the base for producing adequate models of the solar cycle with the purpose to predict the level of solar activity. Since December 1995 the Michelson Doppler Imager (MDI) on board of the Solar and Heliospheric Observatory (SOHO) provides full disk magnetograms and synoptic maps which cover the period of solar cycle 23 and the current minimum. In this paper, I review the following important topics with a focus on the dynamics of the solar magnetic field. The synoptic structure of the solar cycle; the birth of the solar cycle (overlapping cycles 23 and 24); the relationship of the photospheric magnetic activity and the EUV solar corona, polar magnetic fields and dynamo theory (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]